|Capitalized names represent GLERL authors.|
Ahmed, S., C.D. Troy, and N. HAWLEY. Spatial structure of internal Poincare waves in Lake Michigan. Environmental Fluid Mechanics 14(5):1229-1249 (DOI:10.1007/s10652-013-9294-3) (2014).
In this paper we examine the characteristics of near-inertial internal Poincaré waves in Lake Michigan (USA) as discerned from field experiments and hydrodynamic simulations. The focus is on the determination of the lateral and vertical structure of the waves. Observations of near-inertial internal wave properties are presented from two field experiments in southern Lake Michigan conducted during the years 2009 and 2010 at Michigan City (IN, USA) and Muskegon (MI, USA), respectively. Spectra of thermocline displacements and baroclinic velocities show that kinetic and potential baroclinic energy is dominated by near-inertial internal Poincaré waves. Vertical structure discerned from empirical orthogonal function analysis shows that this energy is predominantly vertical mode 1. Idealized hydrodynamic simulations using stratifications from early summer (June), mid-summer (July) and fall (September) identify the basin-scale internal Poincaré wave structure as a combination of single- and two-basin cells, similar to those identified in Lake Erie by Schwab, with near-surface velocities largest in the center of the northern and southern basins. Near inertial bottom kinetic energy is seen to have roughly constant magnitude over large swathes across the basin, with higher magnitude in the shallower areas like the Mid-lake Plateau, as compared with the deep northern and southern basins. The near-bottom near-inertial kinetic energy when mapped appears similar to the bottom topography map. The wave-induced vertical shear across thermocline is concentrated along the longitudinal axis of the lake basin, and both near-bottom velocities and thermocline shear are reasonably explained by a simple conceptual model of the expected transverse variability.
Alves, J.H., A. Chawla, H.L. Tolman, D.J. SCHWAB, G.A. LANG, and G. Mann. The operational implementation of a Great Lakes wave forecasting system at NOAA/NCEP. Weather and Forecasting 29(6):1473-1497 (DOI:10.1175/WAF-D-12-00049.1) (2014). https://www.glerl.noaa.gov/pubs/fulltext/2014/20140069.pdf
The development of a Great Lakes wave forecasting system at NOAA’s National Centers for Environmental Prediction (NCEP) is described. The system is an implementation of the WAVEWATCHIII model, forced with atmospheric data from NCEP’s regional Weather Research and Forecasting (WRF) Model [the North American Mesoscale Model (NAM)] and the National Digital Forecast Database (NDFD). Reviews are made of previous Great Lakes wave modeling efforts. The development history of NCEP’s Great Lakes wave forecasting system is presented. A performance assessment is made of model wind speeds, as well as wave heights and periods, relative to National Data Buoy Center (NDBC) measurements. Performance comparisons are made relative to NOAA’s Great Lakes Environmental Research Laboratory (GLERL) wave prediction system. Results show that 1- and 2-day forecasts from NCEP have good skill in predicting wave heights and periods. NCEP’s system provides a better representation of measured wave periods, relative to the GLERL model in most conditions. Wave heights during storms, however, are consistently underestimated by NCEP’s current operational system, whereas the GLERL model provides close agreement with observations. Research efforts to develop new wave-growth parameterizations and overcome this limitation have led to upgrades to the WAVEWATCH III model, scheduled to become operational at NCEP in 2013. Results are presented from numerical experiments made with the new wave-model physics, showing significant improvements to the skill of NCEP’s Great Lakes wave forecasting system in predicting storm wave heights.
Angeler, D.G., C.R. Allen, C. Barichievy, T. Eason, A.S. Garmestani, N.A.J. Graham, D. Granholm, L. Gunderson, M. Knutson, K.L. Nash, R.J. Nelson, M. Nystrom, T. Spanbauer, C.A. STOW, and S.M. Sundstrom. Management applications of discontinuity theory. Journal of Applied Ecology:11 pp. (DOI:10.1111/1365-2664.12494) (2015).
(1) Human impacts on the environment are multifaceted and can occur across distinct spatiotemporal scales. Ecological responses to environmental change are therefore difficult to predict, and entail large degrees of uncertainty. Such uncertainty requires robust tools for management to sustain ecosystem goods and services and maintain resilient ecosystems. (2) We propose an approach based on discontinuity theory that accounts for patterns and processes at distinct spatial and temporal scales, an inherent property of ecological systems. Discontinuity theory has not been applied in natural resource management and could therefore improve ecosystem management because it explicitly accounts for ecological complexity. (3) Synthesis and applications. We highlight the application of discontinuity approaches for meeting management goals. Specifically, discontinuity approaches have significant potential to measure and thus understand the resilience of ecosystems, to objectively identify critical scales of space and time in ecological systems at which human impact might be most severe, to provide warning indicators of regime change, to help predict and understand biological invasions and extinctions and to focus monitoring efforts. Discontinuity theory can complement current approaches, providing a broader paradigm for ecological management and conservation.
Arhonditsis, G.B., C.A. STOW, Y.R. Rao, and G. Perhar. What has been accomplished twenty years after the Oreskes et al. (1994) critique? Current state and future perspectives of environmental modeling in the Great Lakes. Journal of Great Lakes Research 40(Supplement 3):1-7 (DOI:10.1016/j.jglr.2014.11.002) (2014).
With well over 1000 citations, the Oreskes et al. (1994) paper stands out as one of the classical critiques of the veracity of the scientific methodology of models in earth sciences, arguing that the validation of models that deal with natural systems is inherently impossible. Going beyond the controversy of the “technical versus philosophical” meaning of validation, this viewpoint reflects the important notion that model outputs should be viewed through the prism of the underlying assumptions and that good model performance in one or more settings is not evidence for general applicability, but rather the start of a perpetual race for predictive confirmation. While the Oreskes et al.'s (1994) critique has been a defining moment of the broader appreciation of the challenges surrounding a model validation exercise the documented inadequacy of many models to address important societal issues reflects the fact that the field has advanced without the healthy dose of introspection required to obtain good science. An evidence of the latter assertion is the inconsistency that still characterizes the environmental modeling practice with respect to the methodological steps typically followed (Arhonditsis and Brett, 2004; Arhonditsis et al., 2006; Stow et al., 2009; Robson, 2014; Wellen et al., submitted for publication). After more than four decades of active modeling in the context of environmental management and policy analysis, many of the published aquatic ecosystem and watershed modeling studies still fail to report the results of predictive confirmation, goodness of fit statistics, and uncertainty analysis in the broader sense.
BAI, X., H. HU, J. WANG, Y. Yu, E. Cassano, and J. Maslanik. Responses of surface heat flux, sea ice, and ocean dynamics in the Chukchi-Beaufort Sea to storm passages during winter 2006/2007: A numerical study. Deep Sea Research I 102:101-117 (DOI:10.1016/j.dsr.2015.04.008) (2015).
This study investigates storm impacts on sea ice, oceanic dynamics, and surface heat flux in the Chukchi–Beaufort Seas using a coupled ice–ocean model (CIOM). Two types of storms affect the study area: Arctic-born cyclones and north-moving Aleutian lows, which lead to strong westerly and easterly winds, respectively. Driven by 6-hourly forcing, the CIOM successfully reproduced the storm impacts. Simulated sea ice movements are comparable to the satellite observations. Storms usually result in fast-moving ice, which is faster than the speed of the surface water, and the gap between sea ice and surface water speed increases with wind speed. Storms can alter the pathways of the Pacific inflow water: with westerly winds, the Pacific inflow water goes no further than the latitude of Wrangel Island, while with easterly winds the Pacific inflow water can flow northward into the interior Arctic basin. Strong easterly winds associated with north-moving Aleutian lows reverse the Alaskan Coastal Current and the Bering Slope Current, and induce upwelling along the north Alaska coast. Westerly winds associated with Arctic-born cyclones act in an opposite way. During the storms, heat loss to the atmosphere is about twice that of normal conditions, which is mainly attributed to increases of the sensible and latent heat fluxes over the open water. Heat loss over ice was quite stable with some small fluctuations in response to the storms.
BAI, X., J. WANG, J. Austin, D.J. SCHWAB, R.A. ASSEL, A.H. CLITES, J.F. BRATTON, M.C. COLTON, J. Lenters, B.M. LOFGREN, T. Wohlleben, S. Helfrich, H.A. VANDERPLOEG, L. LUO, and G.A. LESHKEVICH. A record-breaking low ice cover over the Great Lakes during winter 2011/2012: Combined effects of a strong positive NAO and La Nina. Climate Dynamics 44(5-6):1187-1213 (DOI:10.1007/s00382-014-2225-2) (2015).
A record-breaking low ice cover occurred in the North American Great Lakes during winter 2011/2012, in conjunction with a strong positive Arctic Oscillation/ North Atlantic Oscillation (AO/NAO) and a La Nina event. Large-scale atmosphere circulation in the Pacific/ North America (PNA) region reflected a combined signal of La Nina and NAO. Surface heat flux analysis shows that sensible heat flux contributed most to the net surface heat flux anomaly. Surface air temperature is the dominant factor governing the interannual variability of Great Lakes ice cover. Neither La Nina nor NAO alone can be responsible for the extreme warmth; the typical midlatitude response to La Nina events is a negative PNA pattern, which does not have a significant impact on Great Lakes winter climate; the positive phase of NAO is usually associated with moderate warming. When the two occurred simultaneously, the combined effects of La Nina and NAO resulted in a negative East Pacific pattern with a negative center over Alaska/Western Canada, a positive center in the eastern North Pacific (north of Hawaii), and an enhanced positive center over the eastern and southern United States. The overall pattern prohibited the movement of the Arctic air mass into mid-latitudes and enhanced southerly flow and warm advection from the Gulf of Mexico over the eastern United States and Great Lakes region, leading to the record-breaking low ice cover. It is another climatic pattern that can induce extreme warming in the Great Lakes region in addition to strong El Nino events. A very similar event occurred in the winter of 1999/2000. This extreme warm winter and spring in 2012 had significant impacts on the physical environment, as well as counterintuitive effects on phytoplankton abundance.
Bootsma, H.A., M.D. ROWE, C.N. Brooks, and H.A. VANDERPLOEG. Commentary: The need for model development related to Cladophora and nutrient management in Lake Michigan. Journal of Great Lakes Research 41:9 pp. (DOI:10.1016/j.jglr.2015.03.023) (2015).
In the past 10 to 15 years, excessive growth of Cladophora and other attached algae in the nearshore regions of Lake Michigan has re-emerged as an important resource management issue. This paper considers the question, “What information is needed to predict the response of Cladophora production in Lake Michigan to management variables, such as nutrient loading, and to additional environmental variables that are outside of management control?” Focusing on Lake Michigan, while drawing on the broader literature, we review the current state of information regarding 1) models of Cladophora growth, 2) models that simulate the physical environment, 3) models that simulate nearshore and whole-lake nutrient dynamics, with a specific focus on the role of dreissenid mussels, and 4) monitoring of Cladophora abundance. We conclude that while substantial progress has been made, considerable additional research is required before reliable forecasts of Cladophora response to nutrient loads and other environmental variables are possible. By providing a detailed outline of this complex, multidisciplinary problem, we hope that this paper will aid in coordinating collaborative research efforts toward the development of useful predictive models.
BURTON, G.A. Losing sight of science in the regulatory push to ban microbeads from consumer products and industrial use. Integrated Environmental Assessment and Management 11(3):346-347 (DOI:10.1002/ieam.1645) (2015).
Here we go again. Last summer, the state of Illinois was the first to ban tiny plastic microbeads in cosmetics, such as face wash. State legislators claimed the ban was a necessary response to what researchers and environmental groups claim is a serious environmental threat and the US Environmental Protection Agency (USEPA) has labeled as $13 billion annually in damages to marine life. On March 4 of this year, Illinois Congressmen Upton and Pallone introduced House Bill 1321 “to prohibit the sale or distribution of cosmetics containing synthetic plastic microbeads.” Similar measures are now pending in 13 states and in the US Congress. New York’s Attorney General Schneiderman, supported by Senator Gillibrand and a host of environmental groups, has proposed legislation to ban microbeads in cosmetics citing a need to “restore and protect New York’s waters.” Similar legislative efforts are underway in the European Union. It is rare when science and politics are on the same page, and this latest example of the rush to regulate is no exception.
Cha, Y.K., and C.A. STOW. Mining web-based data to assess public response to environmental events. Environmental Pollution 198:97-99 (DOI:10.1016/j.envpol.2014.12.027) (2015).
We explore how the analysis of web-based data, such as Twitter and Google Trends, can be used to assess the social relevance of an environmental accident. The concept and methods are applied in the shutdown of drinking water supply at the city of Toledo, Ohio, USA. Toledo's notice, which persisted from August 1 to 4, 2014, is a high-profile event that directly influenced approximately half a million people and received wide recognition. The notice was given when excessive levels of microcystin, a byproduct of cyanobacteria blooms, were discovered at the drinking water treatment plant on Lake Erie. Twitter mining results illustrated an instant response to the Toledo incident, the associated collective knowledge, and public perception. The results from Google Trends, on the other hand, revealed how the Toledo event raised public attention on the associated environmental issue, harmful algal blooms, in a long-term context. Thus, when jointly applied, Twitter and Google Trend analysis results offer complementary perspectives. Web content aggregated through mining approaches provides a social standpoint, such as public perception and interest, and offers context for establishing and evaluating environmental management policies.
Cooke, R.M., M.E. Wittmann, D.M. Lodge, J.D. Rothlisberger, E.S. RUTHERFORD, H. ZHANG, and D.M. MASON. Out-of-sample validation for structured expert judgment of Asian Carp establishment in Lake Erie. Integrated Environmental Assessment and Management 10(4):522-528 (2014). https://www.glerl.noaa.gov/pubs/fulltext/2014/20140047.pdfStructured expert judgment (SEJ) is used to quantify the uncertainty of nonindigenous fish (bighead carp [Hypophthalmichthys nobilis] and silver carp [H. molitrix]) establishment in Lake Erie. The classical model for structured expert judgment model is applied. Forming a weighted combination (called a decision maker) of experts' distributions, with weights derived from performance on a set of calibration variables from the experts' field, exhibits greater statistical accuracy and greater informativeness than simple averaging with equal weights. New methods of cross validation are applied and suggest that performance characteristics relative to equal weighting could be predicted with a small number (1–2) of calibration variables. The performance based decision maker is somewhat degraded on outsample prediction, but remained superior to the equal weight decision maker in terms of statistical accuracy and informativeness.
David, S.R., R.S. Kik, J.S. Diana, E.S. RUTHERFORD, and M.J. Wiley. Evidence of countergradient variation in growth of Spotted Gars from core and peripheral populations. Transactions of the American Fisheries Society 144(4):837-850 (DOI:10.1080/00028487.2015.1040523) (2015).
Peripheral populations occupy the edge of a species’ range and may exhibit adaptations to potentially “harsher” marginal environments compared with core populations. The peripheral population of Spotted Gar Lepisosteus oculatus in the Great Lakes basin represents the northern edge of the species’ range and is completely disjunct from the core Mississippi River basin population. Age-0 Spotted Gars from the peripheral population experience a growing season approximately half that of the core population but reach similar sizes by winter, suggesting potential for countergradient variation in growth, i.e. an evolutionary response to an environmental gradient such as latitude to compensate for the usual phenotypic effect of that gradient. In this study we used two common garden experiments to investigate potential countergradient variation in growth of young-of-year Spotted Gars from peripheral populations in comparison with those from core populations. Our first experiment showed that in a common environment under temperatures within the first growing season (22–24_C), Spotted Gars from the peripheral population had significantly higher growth rates than those from the core population. Final Spotted Gar weight–length ratio was also higher in the peripheral versus core population. In our second experiment, under three temperature treatments (16, 23, and 30_C), maximum growth occurred at the highest temperature, whereas growth ceased at the lowest temperature for both populations. These results suggest that important genetic and physiological differences could exist between the two population groups, consistent with countergradient variation. Our findings indicate that countergradient growth variation can occur even in relatively slowly evolving fishes, such as gars (family Lepisosteidae), and that protection of peripheral populations should be a key component of fish conservation planning.
DAVIS, T.W., G.S. Bullerjahn, T. Tuttle, R.M. McKay, and S.B. Watson. Effects of increasing nitrogen and phosphorus concentrations on phytoplankton community growth and toxicity during Planktothrix blooms in Sandusky Bay, Lake Erie. Environmental Science & Technology 49:7197-7207 (DOI:10.1021/acs.est.5b00799) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150039.pdf
Sandusky Bay experiences annual toxic cyanobacterial blooms dominated by Planktothrix agardhii / suspensa. To further understand the environmental drivers of these events, we evaluated changes in the growth response and toxicity of the Planktothrix -dominated blooms to nutrient amendments with orthophosphate (PO 4 ) and inorganic and organic forms of dissolved nitrogen (N; ammonium (NH 4 ), nitrate (NO 3 ) and urea) over the bloom season (June − October). We complemented these with a metagenomic analysis of the planktonic microbial community. Our results showed that bloom growth and microcystin (MC) concentrations responded more frequently to additions of dissolved N than PO 4, and that the dual addition of NH 4 +PO 4 and Urea + PO 4 yielded the highest MC concentrations in 54% of experiments. Metagenomic analysis confirmed that P. agardhii / suspensa was the primary MC producer. The phylogenetic distribution of nif H revealed that both heterocystous cyanobacteria and heterotrophic proteobacteria had the genetic potential for N 2 fixation in Sandusky Bay. These results suggest that as best management practices are developed for P reductions in Sandusky Bay, managers must be aware of the negative implications of not managing N loading into this system as N may significantly impact cyanobacterial bloom size and toxicity.
Foley, C.J., G.J. Bowen, T.F. NALEPA, M.S. Sepulveda, and T.O. Hook. Stable isotope patterns of benthic organisms from the Great Lakes region indicate variable dietary overlap of Diporeia spp. and dreissenid mussels. Canadian Journal of Fisheries and Aquatic Sciences 71:1784-1795 (DOI:10.1139/cjfas-2013-0620) (2014). https://www.glerl.noaa.gov/pubs/fulltext/2014/20140050.pdf
Competition between native and invasive species may bring about a suite of ecological and evolutionary outcomes, including local extirpations. In the Laurentian Great Lakes, competition for food may explain the dramatic decline of Diporeia spp. amphipods following the introduction of dreissenid mussels. This hypothesis has not been confirmed, in part because dreissenids and Diporeia appear to co-exist and flourish in other systems, including the Finger Lakes of New York. We used carbon, nitrogen, hydrogen, and oxygen stable isotope ratios to examine resource use by Diporeia from three spatially distinct populations (Lake Michigan, Lake Superior, and Cayuga Lake), dreissenids from areas where they co-occur with Diporeia (Lake Michigan and Cayuga Lake), and Diporeia from Lake Michigan collected before and after dreissenid invasion (1986–2009). Our results suggest that dreissenids may affect resource use by Diporeia in areas of co-occurrence, but the extent to which those effects are positive or negative is unclear. Terrestrial inputs may provide an important subsidy for Diporeia populations in small systems but may not be substantial enough in the Great Lakes to ensure that both taxa thrive.
Fraker, M.E., E.J. ANDERSON, R.M. Brodnik, L. Carreon-Martinez, K.M. DeVanna, B.J. Fryer, D.D. Heath, J.M. Reichert, and S.A. Ludsin. Particle backtracking improves breeding subpopulation discrimination and natal-source identification in mixed populations. PLOS One 10(3):24 pp. (DOI:10.1371/journal.pone.0120752) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150014.pdf
We provide a novel method to improve the use of natural tagging approaches for subpopulation discrimination and source-origin identification in aquatic and terrestrial animals with a passive dispersive phase. Our method integrates observed site-referenced biological information on individuals in mixed populations with a particle-tracking model to retrace likely dispersal histories prior to capture (i.e., particle backtracking). To illustrate and test our approach, we focus on western Lake Erie’s yellow perch (Perca flavescens) population during 2006–2007, using microsatellite DNA and otolith microchemistry from larvae and juveniles as natural tags. Particle backtracking showed that not all larvae collected near a presumed hatching location may have originated there, owing to passive drift during the larval stage that was influenced by strong river- and wind-driven water circulation. Re-assigning larvae to their most probable hatching site (based on probabilistic dispersal trajectories from the particle backtracking model) improved the use of genetics and otolith microchemistry to discriminate among local breeding subpopulations. This enhancement, in turn, altered (and likely improved) the estimated contributions of each breeding subpopulation to the mixed population of juvenile recruits. Our findings indicate that particle backtracking can complement existing tools used to identify the origin of individuals in mixed populations, especially in flow-dominated systems.
Fraker, M.E., E.J. ANDERSON, C. May, K.-Y. Chen, J.J. Davis, K.M. DeVanna, M.R. DuFour, E.A. Marschall, C.M. Mayer, J.G. Miner, K.L. Pangle, J.J. Pritt, E.F. Roseman, J.T. Tyson, Y. Zhao, and S.A. Ludsin. Stock-specific advection of larval walleye (Sander vitreus) in western Lake Erie: Implications for larval growth, mixing, and stock discrimination. Journal of Great Lakes Research 41:16 (DOI:doi:10.1016/j.jglr.2015.04.008) (2015).
Physical processes can generate spatiotemporal heterogeneity in habitat quality for fish and also influence the overlap of pre-recruit individuals (e.g., larvae) with high-quality habitat through hydrodynamic advection. In turn, individuals from different stocks that are produced in different spawning locations or at different times may experience dissimilar habitat conditions, which can underlie within- and among-stock variability in larval growth and survival. While such physically-mediated variation has been shown to be important in driving intra- and inter-annual patterns in recruitment in marine ecosystems, its role in governing larval advection, growth, survival, and recruitment has received less attention in large lake ecosystems such as the Laurentian Great Lakes. Herein, we used a hydrodynamic model linked to a larval walleye (Sander vitreus) individual-based model to explore how the timing and location of larval walleye emergence from several spawning sites in western Lake Erie (Maumee, Sandusky, and Detroit rivers; Ohio reef complex) can influence advection pathways and mixing among these local spawning populations (stocks), and how spatiotemporal variation in thermal habitat can influence stock-specific larval growth. While basin-wide advection patterns were fairly similar during 2011 and 2012, smaller scale advection patterns and the degree of stock mixing varied both within and between years. Additionally, differences in larval growth were evident among stocks and among cohorts within stocks which were attributed to spatiotemporal differences in water temperature. Using these findings, we discuss the value of linked physical–biological models for understanding the recruitment process and addressing fisheries management problems in the world's Great Lakes.
FRY, L.M., A.D. GRONEWOLD, V. Fortin, S. Buan, A.H. CLITES, C. Luukkonen, D. Hotsschlag, D. L., T.S. HUNTER, F. Seglenieks, D. Durnford, M. Dimitrijevic, C. Subich, E. Klyszejko, K. KEA, and P. Restrepo. The Great Lakes Runoff Intercomparison Project, Phase 1: Lake Michigan (GRIP-M). Journal of Hydrology 519(Part D):3448-3465 (DOI:10.1016/j.jhydrol.2014.07.021) (2014).
We assembled and applied five models (one of which included three different configurations) to the Lake Michigan basin to improve our understanding of how differences in model skill at simulating total runoff to Lake Michigan relate to model structure, calibration protocol, model complexity, and assimilation (i.e. replacement of simulated discharge with discharge observations into historical simulations), and evaluate historical changes in runoff to Lake Michigan. We found that the performance among these models when simulating total runoff to the lake varied relatively little, despite variability in model structure, spatial representation, input data, and calibration protocol. Relatively simple empirical, assimilative models, including the National Oceanic and Atmospheric Administration (NOAA) Great Lakes Environmental Research Laboratory (GLERL) area ratio-based model (ARM) and the United States Geological Survey (USGS) Analysis of Flows in Networks of CHannels (AFINCH) model, represent efficient and effective approaches to propagating discharge observations into basin-wide (including gaged and ungaged areas) runoff estimates, and may offer an opportunity to improve predictive models for simulating runoff to the Great Lakes. Additionally, the intercomparison revealed that the median of the simulations from non-assimilative models agrees well with assimilative models, suggesting that using a combination of different methodologies may be an appropriate approach for estimating runoff into the Great Lakes. We then applied one assimilative model (ARM) to the Lake Michigan basin and found that there was persistent reduction in the amount of precipitation that becomes runoff following 1998, corresponding to a period of persistent low Lake Michigan water levels. The study was conducted as a first phase of the Great Lakes Runoff Intercomparison Project, a regional binational collaboration that aims to systematically and rigorously assess a variety of models currently used (or that could readily be adapted) to simulate basin-scale runoff to the North American Laurentian Great Lakes.
GLYSHAW, P.W., C.M. Riseng, T.F. Nalepa, and S.A. POTHOVEN. Temporal trends in nutritional state and reproduction of quagga mussels (Dreissena rostriformis bugensis) in southern Lake Michigan. Journal of Great Lakes Research 41(Supplement 2):11 pp. (DOI:10.1016/j.jglr.2015.08.006) (2015).
Currently little is known about the condition and spawning patterns of quagga mussels (Dreissena rostriformis bugensis) in deeper, consistently cold regions of the Great Lakes. This lack of information limits our ability to predict the future expansion of D. r. bugensis in the offshore regions of the Great Lakes and other large, deep lakes. We collected quagga mussels on a monthly basis in 2013 (April–September) at three established sites along a depth transect (25, 45, and 93 m) in southern Lake Michigan and calculated a condition index (CI), a ratio of dry soft tissueweight to internal shell capacity, to assess condition, and a gametogenic index to assess reproductive activity. We also measured size–frequency, density, and biomass in March, July, and October. Condition was consistently highest at 25 m, population biomass and average shell length were highest at 45 m, and density was highest at 93 m. At all three depths, CI decreased with increasing shell length suggesting that food availability may be limiting for larger individuals. Mussels at 45 m spawned earliest with over 50% spent by July while mussels at 93 m began spawning in August.Mussels at 25 m had not yet spawned by September. Long-term trends in density indicate that D. r. bugensis populations continued to expand at the 93 m site but may be stabilizing at 25 m and 45 m. Consistent with density trends, CI at 25 m and 45 m was lower than in 2004 and 2008.
GRONEWOLD, A.D., E.J. ANDERSON, B.M. LOFGREN, P.D. Blanken, J. WANG, J.P. SMITH, T.S. HUNTER, G.A. LANG, C.A. STOW, D. BELETSKY, and J.F. BRATTON. Impacts of extreme 2013-2014 winter conditions on Lake Michigan's fall heat content, surface temperature, and evaporation. Geophysical Research Letters 42:7 pp. (DOI:10.1002/2015GL063799) (2015).
Since the late 1990s, the Laurentian Great Lakes have experienced persistent low water levels and above average over-lake evaporation rates. During the winter of 2013–2014, the lakes endured the most persistent, lowest temperatures and highest ice cover in recent history, fostering speculation that over-lake evaporation rates might decrease and that water levels might rise. To address this speculation, we examined interseasonal relationships in Lake Michigan’s thermal regime. We find pronounced relationships between winter conditions and subsequent fall heat content, modest relationships with fall surface temperature, but essentially no correlation with fall evaporation rates. Our findings suggest that the extreme winter conditions of 2013–2014 may have induced a shift in Lake Michigan’s thermal regime and that this shift coincides with a recent (and ongoing) rise in Great Lakes water levels. If the shift persists, it could (assuming precipitation rates remain relatively constant) represent a return to thermal and hydrologic conditions not observed on Lake Michigan in over 15 years.
GRONEWOLD, A.D., A.H. CLITES, J. Bruxer, K.A. Kompoltowicz, J.P. SMITH, T.S. HUNTER, and C. Wong. Water levels surge on the Great Lakes. Eos 96(6):7 pp. (DOI:10.1029/2015EO026023) (2015). https://eos.org/project-updates/water-levels-surge-on-great-lakes
Water levels on Lake Superior and Lake Michigan-Huron (Lake Michigan and Lake Huron are commonly viewed as a single lake from a long-term hydrological perspective), the two largest lakes on Earth by surface area, rose at a remarkable rate over the past 2 years. The recent surge represents one of the most rapid rates of water level change on the Great Lakes in recorded history and marks the end of an unprecedented period of below-average water levels that began in 1998.
GRONEWOLD, A.D., A.H. CLITES, and L. Rear-McLaughlin. Great Lakes water levels: Monitoring change in Earth's largest surface freshwater system. In Clear Waters. New York Water Environment Association, Inc., Syracuse, NY, 16-18 pp. (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150036.pdf
The Great Lakes, their connecting waterways and their watersheds, comprise the largest surface freshwater system on Earth. They are a dominant physical feature of North America and form part of the political boundary between the U.S. and Canada. The Great Lakes contain nearly 20 percent of the workd's fresh surfce water and have a coastline longer than the east of west coast of the US. One-third of the North American population lives within the Great Lakes watershed. The lakes provide drinking water to 40 million people as well as abundant aquatic recreation and beauty.
Gyawali, R., D.W. Watkins, V.W. Griffis, and B.M. LOFGREN. Energy budget considerations for hydro-climatic impact assessment in Great Lakes watersheds. Journal of Great Lakes Research 40(4):940-948 (DOI:10.1016/j.jglr.2014.09.005) (2014).
Given the large share of the water budget contributed by evapotranspiration (ET), accurately estimating ET is critical for hydro-climate change studies. Routinely, hydrologic models use temperature proxy relationships to estimate potential evapotranspiration (PET) when forced using GCM/RCM projections of precipitation and temperature. A limitation of this approach is that the temperature proxy relationships do not account for the conservation of energy needed to estimate ET consistently in climate change scenarios. In particular, PET methods using temperature as a proxy fail to account for the negative feedback of ET on surface temperature. Using several GCM projections and a hydrologic model developed for the Great Lakes basin watersheds, the NOAA Large Basin Runoff Model (LBRM), the importance of maintaining a consistent energy budget in hydrologic and climate models is demonstrated by comparing runoff projections from temperature proxy and energy conservation methods. Differences in hydrologic responses are related to watershed characteristics, hydrologic model parameters and climate variables. It is shown that the temperature proxy approach consistently leads to prediction of relatively large and potentially unrealistic reductions in runoff. Therefore, hydrologic projections adhering to energy conservation principles are recommended for use in climate change impact studies.
He, J.X., J.R. Bence, C.P. Madenjian, S.A. POTHOVEN, N.E. Dobiesz, D.G. Fielder, J.L. Johnson, M.P. Ebener, A.R. Cottrill, L.C. Mohr, and S.R. Koproski. Coupling age structured stock assessment and fish bioenergetics models: A system of time-varying models for quantifying piscivory patterns during the rapid trophic shift in the main basin of Lake Huron. Canadian Journal of Fisheries and Aquatic Sciences 72(1):7-23 (DOI:10.1139/cjfas-2014-0161) (2015).
We quantified piscivory patterns in the main basin of Lake Huron during 1984–2010 and found that the biomass transfer from prey fish to piscivores remained consistently high despite the rapid major trophic shift in the food webs. We coupled age-structured stock assessment models and fish bioenergetics models for lake trout (Salvelinus namaycush), Chinook salmon (Oncorhynchus tshawytscha), walleye (Sander vitreus), and lake whitefish (Coregonus clupeaformis). The model system also included time-varying parameters or variables of growth, length–mass relations, maturity schedules, energy density, and diets. These time-varying models reflected the dynamic connections that a fish cohort responded to year-to-year ecosystem changes at different ages and body sizes. We found that the ratio of annual predation by lake trout, Chinook salmon, and walleye combined with the biomass indices of age-1 and older alewives (Alosa pseudoharengus) and rainbow smelt (Osmerus mordax) increased more than tenfold during 1987–2010, and such increases in predation pressure were structured by relatively stable biomass of the three piscivores and stepwise declines in the biomass of alewives and rainbow smelt. The piscivore stability was supported by the use of alternative energy pathways and changes in relative composition of the three piscivores. In addition, lake whitefish became a new piscivore by feeding on round goby (Neogobius melanostomus). Their total fish consumption rivaled that of the other piscivores combined, although fish were still a modest proportion of their diet. Overall, the use of alternative energy pathways by piscivores allowed the increases in predation pressure on dominant diet species.
HUNTER, T.S., A.H. CLITES, A.D. GRONEWOLD, and K.B. CAMPBELL. Development and application of a North American Great Lakes hydrometeorological database - Part I: Precipitation, evaporation, runoff, and air temperature. Journal of Great Lakes Research 41(1):65-77 (DOI:10.1016/j.jglr.2014.4.12.006) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150006.pdf
Starting in 1983, the National Oceanic and Atmospheric Administration (NOAA) Great Lakes Environmental Research Laboratory (GLERL) has been developing and maintaining a historical time series of North American Great Lakes basin-scale monthly hydrometeorological data. This collection of data sets, which we hereafter refer to as the NOAA-GLERL monthly hydrometeorological database (GLM-HMD), is, to our knowledge, the first (and perhaps still the only) to assimilate hydrometeorological measurements into model simulations for each of the major components of the water budget across the entirety (i.e., both United States and Canadian portions) of the Great Lakes basin for a period of record dating back to the early and mid 1900s. Here, we describe the development of data sets in the first (GLM-HMD-I) of two subsets of the GLM-HMD including basin-scale estimates of over-lake and over-land precipitation and air temperature, runoff, and over-lake evaporation. Our synthesis of the GLM-HMD-I includes a summary of the monitoring network associated with each variable and an indication of how each monitoring network has changed over time. We conclude with two representative applications of the GLM-HMD aimed at advancing understanding of seasonal and long-term changes in Great Lakes regional meteorology and climatology. These two examples implicitly reflect the historical utility of the GLM-HMD in numerous previous studies, and explicitly demonstrate its potential utility in ongoing and future regional hydrological science and climate change research.
IVAN, L.N., D.G. Fielder, M.V. Thomas, and T.O. Hook. Changes in the Saginaw Bay, Lake Huron, fish community from 1970-2011. Journal of Great Lakes Research 40:922-933 (DOI:10.1016/j.jglr.2014.09.002) (2014).
Many aquatic ecosystems experience concurrent anthropogenic stressors that can have complex impacts on fish communities. Limited data and temporal associations among environmental stressors may confound the ability to attribute community-level impacts to single or multiple stressors. Instead, quantitative description of temporal changes in fish communities may shed light on the cumulative and individual impacts of diverse stressors. Saginaw Bay, Lake Huron, has experienced diverse anthropogenic stressors that have been inconsistently quantified over time. We used resampling and multivariate approaches to analyze long-term trawl data to describe how fish community patterns changed in Saginaw Bay from1970–2011. Total, native, and moderately tolerant fish species richness generally increased from 1970–2011. Dynamic factor analysis and nonmetric multidimensional scaling revealed that fish community structure changed from 1970–2011 and that relative abundances of many fish species increased. In general, increases in richness and CPUE were correlated with decreases in total phosphorus, chl a, and water levels. In addition, breakpoint analyses revealed shifts in species richness in the mid-1980s and 1999. Temporal patterns are consistent with the hypothesis that the Saginaw Bay fish community has changed from one dominated by species tolerant of eutrophy to one with more sensitive species, likely a response to decreased phosphorous loading and resulting changes in water quality. More recently (1999–2011), richness and relative abundance of many fish species in Saginaw Bay declined, a pattern potentially reflective of larger food-web transitions in both Saginaw Bay and open Lake Huron.
IVAN, L.N., and T.O. Hook. Energy allocation strategies of young temperate fish: An eco-genetic modeling approach. Canadian Journal of Fisheries and Aquatic Sciences 72(8):1243-1258 (DOI:10.1139/cjfas-2014-0197) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150034.pdf
We use an individual-based eco-genetic model to explore the relative selective pressures of size-dependent predation, overwinter mortality, and density-dependent energy acquisition in structuring plastic and adaptive energy allocation during the first year of life of a temperate fish population. While several patterns emerging from a suite of eco-genetic model simulations were consistent with past theoretical models and empirical evaluations of energy allocation by young fishes, results also highlight the utility of eco-genetic models for simultaneous consideration of plastic and adaptive processes. Across simulations, variation in genetic control of energy allocation was limited during very early ontogeny when size-dependent predation pressure was particularly high. While this stabilizing selection on energy allocation diminished later in the growing season, predation, overwinter mortality, and density-dependent processes simultaneously structured energy partitioning later in ontogeny through the interactive influence of plastic and adaptive processes. Specifically, high risk of overwinter mortality and low predation selected for high prioritization of energy storage. We suggest that simulations demonstrate the utility of eco-genetic models for generating null predictions of how selective pressures may structure expression of life history traits, such as early life energy allocation.
Jiang, L., M. Xia, S.A. Ludsin, E.S. RUTHERFORD, D.M. MASON, J.M. Jarrin, and K.L. Pangle. Biophysical modeling assessment of the drivers for plankton dynamics in dreissenid-colonized western Lake Erie. Ecological Modelling 308:18-33 (2015).
Given that phytoplankton and zooplankton communities have served as key ecological indicators of anthropogenic and other perturbations, a high-resolution Finite Volume Coastal Ocean Model (FVCOM) based Integrated Compartment Model (FVCOM-ICM) was implemented to investigate plankton dynamics with the inclusion of dreissenid invasion in Lake Erie, particularly in the most productive western basin. After identifying suitable horizontal and vertical resolutions that allowed for accurate depiction of in-lake nutrient concentrations and plankton biomass, we explored how variation in nutrient (phosphorus, nitrogen) loading and dreissenid mussel density could influence plankton dynamics. Our scenario-testing showed that western Lake Erie’s phytoplankton community appeared more limited by phosphorus than nitrogen on both seasonal and interannual scales with light limitation occurring in the nearshore and Maumee River plume areas. Dreissenid mussel impacts varied temporally, with phytoplankton communities being highly influenced by dreissenid nutrient excretion at times (under low nutrient availability) and dreissenid grazing at other times (under bloom conditions). It was concluded that the effect of zooplankton predation on phytoplankton was stronger than that of dreissenid mussels, and that multiple algal groups could promote the efficiency of nutrient assimilation and the overall plankton production. Additionally, river inputs and wind-driven water circulation were important by causing heterogeneity in habitat conditions through nutrient advection and vertical mixing, and wind-induced surface waves could result in non-negligible down-wind redistribution of plankton biomass, which increased with wind/wave magnitude.
JOSHI, S.J., A. Stevens, and L. Vaccaro. Saginaw Bay Multiple Stressors and Beyond workshop: Summary report. NOAA Technical Memorandum GLERL-166. NOAA Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 28 pp. (2015). https://www.glerl.noaa.gov/pubs/tech_reports/glerl-166/tm-166.pdf
Saginaw Bay has been and continues to be exposed to many stressors from anthropogenic activities, including toxic contaminants, nutrients, sediments, overfishing, exotic species, and declining water levels. In response, the NOAA Great Lakes Environmental Research Laboratory (GLERL), the Cooperative Institute for Limnology and Ecosystems Research (CILER), and other partner institutions began a five-year Saginaw Bay Multiple Stressors Project sponsored by the Center for Sponsored Coastal Ocean Research (CSCOR) in 2007, evaluating the impacts of these stressors and their combined effects on Saginaw Bay and their management implications. With the project coming to an end in 2012, a dialogue with the scientists and representatives from the Michigan Departments of Natural Resources (DNR) and Environmental Quality (DEQ), Michigan Sea Grant, and other organizations was necessary in order to decide how to best convey the project results and prioritize next steps for future research in Saginaw Bay. This dialogue was conducted through an all-day needs assessment workshop with the goal of receiving input and feedback on remaining research and outreach needs in Saginaw Bay and gaining recommendations for continued research to build upon the Multiple Stressors Project. Additionally the workshop aimed at identifying any remaining gaps in research and outreach efforts in Saginaw Bay and to determine where NOAA and Michigan Sea Grant should begin prioritizing research and outreach and education programs. This report describes the results of the workshop including remaining issues and needs identified as well as priorities for future research, and strategies and recommendations for next steps.
Kao, Y.C., C.P. Madenjian, D.B. Bunnell, B.M. LOFGREN, and M. PERROUD. Temperature effects induced by climate change on the growth and consumption by salmonines in Lakes Michigan and Huron. Environmental Biology of Fishes 98:1089-1104 (DOI:10.1007/s10641-014-0352-6) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2014/20140059.pdf
We used bioenergetics models to investigate temperature effects induced by climate change on the growth and consumption by Chinook salmon Oncorhynchus tshawytscha, lake trout Salvelinus namaycush, and steelhead O. mykiss in Lakes Michigan and Huron. We updated biological inputs to account for recent changes in the food webs and used temperature inputs in response to regional climate observed in the baseline period (1964–1993) and projected in the future period (2043–2070). Bioenergetics simulations were run across multiple age-classes and across all four seasons in different scenarios of prey availability. Due to the increased capacity of prey consumption, future growth and consumption by these salmonines were projected to increase substantially when prey availability was not limited. When prey consumption remained constant, future growth of these salmonines was projected to decrease in most cases but increase in some cases where the increase in metabolic cost can be compensated by the decrease in waste (egestion and excretion) loss. Consumption by these salmonines was projected to increase the most during spring and fall when prey energy densities are relatively high. Such seasonality benefits their future growth through increasing annual gross energy intake. Our results indicated that lake trout and steelhead would be better adapted to the warming climate than Chinook salmon. To maintain baseline growth into the future, an increase of 10 % in baseline prey consumption was required for Chinook salmon but considerably smaller increases, or no increases, in prey consumption were needed by lake trout and steelhead.
Kao, Y.C., C.P. Madenjian, D.B. Bunnell, B.M. LOFGREN, and M. PERROUD. Potential effects of climate change on the growth of fishes from different thermal guilds in Lakes Michigan and Huron. Journal of Great Lakes Research 41:423-435 (DOI:10.1016/j.jglr.2015.03.012) (2015).
We used a bioenergetics modeling approach to investigate potential effects of climate change on the growth of two economically important native fishes: yellow perch (Perca flavescens), a cool-water fish, and lake whitefish (Coregonus clupeaformis), a cold-water fish, in deep and oligotrophic Lakes Michigan and Huron. For assessing potential changes in fish growth, we contrasted simulated fish growth in the projected future climate regime during the period 2043–2070 under different prey availability scenarios with the simulated growth during the baseline (historical reference) period 1964–1993. Results showed that effects of climate change on the growth of these two fishes are jointly controlled by behavioral thermoregulation and prey availability. With the ability of behavioral thermoregulation, temperatures experienced by yellow perch in the projected future climate regime increased more than those experienced by lake whitefish. Thus simulated future growth decreased more for yellow perch than for lake whitefish under scenarios where prey availability remains constant into the future. Under high prey availability scenarios, simulated future growth of these two fishes both increased but yellow perch could not maintain the baseline efficiency of converting prey consumption into body weight. We contended that thermal guild should not be the only factor used to predict effects of climate change on the growth of a fish, and that ecosystem responses to climate change should be also taken into account.
Kopf, A., T.W. DAVIS, and among 154 others. The Ocean Sampling Day consortium. GigaScience 4(27):5 (DOI:10.1186/s13742-015-0066-5) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150038.pdf
Ocean Sampling Day was initiated by the EU-funded Micro B3 (Marine Microbial Biodiversity, Bioinformatics, Biotechnology) project to obtain a snapshot of the marine microbial biodiversity and function of the world’s oceans. It is a simultaneous global mega-sequencing campaign aiming to generate the largest standardized microbial data set in a single day. This will be achievable only through the coordinated efforts of an Ocean Sampling Day Consortium, supportive partnerships and networks between sites. This commentary outlines the establishment, function and aims of the Consortium and describes our vision for a sustainable study of marine microbial communities and their embedded functional traits.
Kult, J.M., L.M. FRY, A.D. GRONEWOLD, and W. Choi. Regionalization of hydrologic response in the Great Lakes basin: Considerations of temporal scales of analysis. Journal of Hydrology 519:2224-2237 (DOI:10.1016/j.jhydrol.2014.09.083) (2014).
Methods for predicting streamflow in areas with limited or nonexistent measures of hydrologic response commonly rely on regionalization techniques, where knowledge pertaining to gauged watersheds is transferred to ungauged watersheds. Hydrologic response indices have frequently been employed in contemporary regionalization research related to predictions in ungauged basins. In this study, we developed regionalization models using multiple linear regression and regression tree analysis to derive relationships between hydrologic response and watershed physical characteristics for 163 watersheds in the Great Lakes basin. These models provide an empirical means for simulating runoff in ungauged basins at a monthly time step without implementation of a rainfall–runoff model. For the dependent variable in these regression models, we used monthly runoff ratio as the indicator of hydrologic response and defined it at two temporal scales: (1) treating all monthly runoff ratios as individual observations, and (2) using the mean of these monthly runoff ratios for each watershed as a representative observation. Application of the models to 62 validation watersheds throughout the Great Lakes basin indicated that model simulations were far more sensitive to the temporal characterization of hydrologic response than to the type of regression technique employed, and that models conditioned on individual monthly runoff ratios (rather than long term mean values) performed better. This finding is important in light of the increased usage of hydrologic response indices in recent regionalization studies. Models using individual observations for the dependent variable generally simulated monthly runoff with reasonable skill in the validation watersheds (median Nash–Sutcliffe efficiency = 0.53, median R2 = 0.66, median magnitude of the deviation of runoff volume = 13%). These results suggest the viability of empirical approaches to simulate runoff in ungauged basins. This finding is significant given the many regions of the world with sparse gauging networks and limited resources for gathering the field data required to calibrate rainfall– runoff models.
Lei, R., H. Xie, J. WANG, M. Lepparanta, I. Jonsdottir, and Z. Zhang. Changes in sea ice concentrations along the Arctic Northeast Passage from 1979 to 2012. Cold Regions Science and Technology 119:132-144 (DOI:10.1016/j.coldregions.2015.08.004) (2015).
Sea ice conditions in the Arctic Northeast Passage (NEP) have changed dramatically in the last four decades, with important impacts on the environment and navigability. In the present study, multisource remote sensing data for 1979–2012 were analyzed to quantify seasonal, interannual, and spatial changes in sea ice conditions along the NEP. Data for October–November showed that spatially averaged ice thickness in the NEP decreased from 1.2–1.3min 2003–2006 to 0.2–0.6min 2011–2012. From 1979 to 2012, the fastest decreasing trend in monthly ice concentration occurred in October (−1.76% per year, P b 0.001), when the ice cover starts to increase. As a result of decreasing multiyear sea ice, thinning ice and delayed freeze-up, the spatially averaged length of open period (ice concentration b 50%) increased from 84 days in the 1980s to 114 days in the 2000s and reached 146 days in 2012. The Kara, Laptev, and East Siberian sectors were relatively inaccessible, especially the sector of 90–110°E around the Vilkitsky Strait. However, because of the thinning sea ice prior to the melt season and the enhanced positive polarity of the summer Arctic Dipole Anomaly, these sectors have become more accessible in recent years. The summer sea ice along the high-latitude sea route (HSR) north of the eastern Arctic islands, with a route distance comparable to the NEP, has also decreased during the last decade with the ice-free period reaching 42 days in 2012. The HSR avoids shallowwaters along the coast, improving access to the Arctic sea route for deeper-draft vessels
Liao, X., Y. Du, H. Zhan, P. Shi, and J. WANG. Summertime phytoplankton blooms and surface cooling in the western south equatorial Indian Ocean. Journal of Geophysical Research - Oceans 119:7687-7704 (DOI:10.1002/2014JC010195) (2015).
Chlorophyll-a (Chla) concentration derived from the Sea viewing Wide field of View sensor (SeaWiFS) data (January 1998 to December 2010) shows phytoplankton blooms in the western south equatorial Indian Ocean (WSEIO) during the summer monsoon. The mechanism that sustains the blooms is investigated with the high-resolution Ocean General Circulation Model for the Earth Simulator (OFES) products. The summer blooms in the WSEIO are separated from the coast; they occur in June, reach their maximum in August, and decay in October. With summer monsoon onset, cross-equatorial wind induces open-ocean upwelling in the WSEIO, uplifting the nutricline. The mixed layer heat budget analysis reveals that both thermal forcing and ocean processes are important for the seasonal variations of SST, especially wind-driven entrainment plays a significant role in cooling the WSEIO. These processes cause nutrient enrichment in the surface layer and trigger the phytoplankton blooms. As the summer monsoon develops, the strong wind deepens the mixed layer; the entrainment thus increases the nutrient supply and enhances the bloom. Horizontal advection associated with the Southern Gyre might also be an important process that sustains the bloom. This large clockwise gyre could advect nutrient-rich water along its route, allowing Chla to bloom in a larger area.
Link, J., D.M. MASON, T. Lederhouse, S. Gaichas, T. Hartley, J. Ianeli, R. Methot, C. Stock, C.A. STOW, and H. Townsend. Report from the Joint OAR-NMFS Modeling Uncertainty Workshop. NOAA Technical Memorandum NMFS-F/SPO-153. NOAA National Marine Fisheries Office of Science and Technology, Silver Spring, MD, 31 pp. (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/NOAA_TM_NMFS-F_SPO-153.pdf
The National Oceanic and Atmospheric Administration’s (NOAA’s) Office of Oceanic and Atmospheric Research (OAR) and National Marine Fisheries Service (NMFS) held a joint workshop April 13–15, 2015, at NOAA’s Great Lakes Environmental Research Laboratory in Ann Arbor, Michigan, to examine methods and means of addressing, reviewing, and presenting uncertainty in ecosystem and living marine resource models and assessments. This workshop explored the range of practices used within OAR, NMFS, and other organizations in the modeling community to deal with uncertainty, developed a set of best practices, and identified recommendations to better address model output uncertainty and improve model skill. A broad range of NOAA’s living marine resource and ecosystem modeling approaches were discussed. Examples from these and related disciplines show a healthy and robust gradient of models along multiple dimensions of complexity. As such, continued model development remains an important research activity and should include evaluations of model uncertainty. Best approaches to address uncertainties depend on the type of model and application. In this context, the workshop focused on model skill evaluation, noting the need for and feasibility of multiple measures. Participants identified 14 best practices at the workshop that will serve ongoing and future efforts to address model uncertainty. A simple “cheat sheet” on matching approaches with specific types of uncertainty across model applications was suggested. This could lead to a template of standard reporting for living marine resource and ecosystem assessment outputs. The benefits of having a common usage of quantitative information to explore model skill would provide the public with a more consistent communication of scientific results and management implications. Some of the key practices that emerged included the use of multi-model inference, adoption of management strategy evaluations, and improved use of communication tools. These formed the basis of eight recommendations specific to model efforts. Overall, cross-disciplinary, cross-organizational meetings like this to coordinate and advance modeling efforts were considered useful and should continue. Next steps recommended are: (1) Seek NOAA leadership support for a full range of quantitative modeling efforts across the spectrum of complexity and disciplinary emphasis in support of living marine resource management mandates. (2) Establish routine and regular venues for the NOAA modeling community to meet and interact. (3) Support and advance cross-line-office and cross-disciplinary (including social science) coordination on model development.
LIU, P.C. Freaque wave occurrences in 2013. Natural Hazards and Earth System Sciences 2:7017-7025 (DOI:10.5194/nhessd-2-7017-2014) (2014). https://www.glerl.noaa.gov/pubs/fulltext/2014/20140063.pdf
Documenting freaque waves when they occurred around the globe in 2013 is based here on news reports on the internet. It was found that there were a total 22 cases of freaque waves in 2013, based on those reported in clearly-defined physically specific environments. There were three cases in the deep ocean, six in nearshore areas, seven on sandy beaches, and seven on rocky shore areas. Note that most of the academic research has been on freaque waves in the deep ocean, which accounts for 13% of all occurrences. The majority of reported occurrences, 87%, are in the nearshore areas or along the beach area. Geographically, these cases are also fairly evenly spread around the globe. As of now, there is no general knowledge regarding the frequency of occurrence of these freaque waves, so that one may assume that 2013 was a customary year for freaque wave occurrences.
LIU, P.C., R. Bouchard, W.E. Rogers, A.V. Babanin, and D.W. Wang. Is there a wind connection to freaque wave occurrences? Natural Hazards and Earth System Sciences 15:1-17 (DOI:10.5194/nhessd-15-1-2015) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150004.pdf
There was a recent freaque wave encounter near Scituate, Massachusetts by a local transport ferry en route from Provincetown to Boston. The encounter resulted in minimal damages, fortunately, and provided us a chance to examine a possible connection between the freaque wave occurrence and the ambient wind field, since the place of encounter was in the vicinity of a NOAA NDBC buoy where wind and wave data were recorded. Here we present a brief analysis. In particular, we found it is plausible that the freaque wave was the result of a wind speed reduction in the wind field that preceded its occurrence.
LOFGREN, B.M. Simulation of atmospheric and lake conditions in the Laurentian Great Lakes region using the Coupled Hydrosphere-Atmosphere Research Model (CHARM). NOAA Technical Memorandum GLERL-165. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 23 pp. (2014). https://www.glerl.noaa.gov/pubs/tech_reports/glerl-165/tm-165.pdf
Greenhouse gas-induced climate change will have notable effects on the Great Lakes region, in the atmosphere, land surfaces, and lakes themselves. Simulations of these effects were carried out using the Coupled Hydrosphere-Atmosphere Research Model (CHARM), driven by output from the Canadian General Circulation Model version 3 (CRCM3) for past and future time periods. This results in increased downward longwave radiation and near-surface air temperature. The air temperature increases during summer have strong spatial minima directly over the lakes that are limited to the lowest model layer and seem to be associated with frequent fog depicted by CHARM. Precipitation is also generally increased, with the most spatially coherent, and among the strongest, increases occurring in the near-shore lake effect zones during winter. Evapotranspiration is generally increased, although only weakly over land, but very strongly over the lakes during winter. Water temperatures are increased and the summer stratification pattern (warmer water overlying colder) is established earlier in the year. Ice cover is diminished and limited to shallow parts of the lakes. Several bugs and shortcomings in CHARM are identified for correction in future development and use
LOFGREN, B.M., and J. Rouhana. Reaffirmation of large biases in a long-used method for projecting changes in Great Lakes water levels. NOAA Technical Memorandum GLERL-167. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 25 pp. (2015). https://www.glerl.noaa.gov/pubs/tech_reports/glerl-167/tm-167.pdf
A method for projecting the water levels of the Laurentian Great Lakes under scenarios of human-caused climate change, used almost to the exclusion of other methods in the past, relies very heavily on the Large Basin Runoff Model (LBRM) as a component for determining the water budget for the lake system. This model uses near-surface air temperature as a primary predictor of evapotranspiration (ET); in addition to previous published work, we show here again that its very high sensitivity to temperature makes it overestimate ET in a way that is highly inconsistent with the fundamental principle of conservation of energy at the land surface. Under the traditional formulation, the quantity that has been called “energy available for evapotranspiration,” which is proportional to what we call “potential evapotranspiration” (PET), is increased by large factors in future scenarios—by a factor of nearly 600 in the Lake Superior basin under forcing by one GCM case, but more typically by factors between 3 and 10. Because of the way that LBRM is formulated and calibrated, these factors can be thought of as corresponding to the factor of increase in solar radiation incident on the Earth, or, more vividly, as the number of Suns present in the sky of the virtual world simulated by LBRM. Therefore, we have created alternative formulations, which we regard as more reflective of what is being simulated by the driving GCMs, for the way that climate change is ingested into the modeling system that includes LBRM. In addition to the energy adjustment method in which PET is increased by an amount proportional to the change in net radiative energy at the surface, we add the Priestley-Taylor method, which augments the energy adjustment method by inclusion of a temperature-dependent factor with rigorous theoretical underpinnings that is a much weaker function of temperature than in the LBRM’s basic formulation, as well as the Clausius-Clapeyron method, in which the PET is increased by an amount proportional to the increase in water vapor capacity of the atmosphere, again a weaker function of temperature than in the LBRM. We establish that all three of these alternative methods show, relative to the traditional method, often astoundingly less PET and less ET, more runoff from the land and net basin supply for the lake basins, and higher lake water levels in the future. The magnitude of these discrepancies is highly correlated with the air temperature change in the driving GCM (larger temperature changes lead to larger discrepancies). Using various methods of estimating the statistical significance, we find that, at minimum, these discrepancies in results are significant at the 99.998% level.
Lynch, A.J., W.W. Taylor, T.D. Beard, and B.M. LOFGREN. Climate change projections for lake whitefish (Coregonus clupeaformis) recruitment in the 1836 Treaty Waters of the upper Great Lakes. Journal of Great Lakes Research 41(2):415-422 (DOI:10.1016/j.jglr.2015.03.015) (2015).
Lake whitefish (Coregonus clupeaformis) is an ecologically, culturally, and economically important species in the Laurentian Great Lakes. Lake whitefish have been a staple food source for thousands of years and, since 1980, have supported the most economically valuable (annual catch value≈US$16.6 million) and productive (annual harvest ≈ 7 million kg) commercial fishery in the upper Great Lakes (Lakes Huron, Michigan, and Superior). Climate changes, specifically changes in temperature, wind, and ice cover, are expected to impact the ecology, production dynamics, and value of this fishery because the success of recruitment to the fishery has been linked with these climatic variables. We used linear regression to determine the relationship between fall and spring air temperature indices, fall wind speed, winter ice cover, and lake whitefish recruitment in 13 management units located in the 1836 Treaty Waters of the Upper Great Lakes ceded by the Ottawa and Chippewa nations, a culturally and commercially important region for the lake whitefish fishery. In eight of the 13 management units evaluated, models including one or more climate variables (temperature, wind, ice cover) explained significantly more variation in recruitment than models with only the stock–recruitment relationship, using corrected Akaike's Information Criterion comparisons (ΔAICc > 3). Isolating the climate–recruitment relationship and projecting recruitment with the Coupled Hydrosphere-Atmosphere Research Model (CHARM) indicated the potential for increased lake whitefish recruitment in the majority of the 1836 Treaty Waters management units. These results can inform adaptive management strategies by providing anticipated implications of climate on lake whitefish recruitment.
Madenjian, C.P., D.B. Bunnell, D.M. Warner, S.A. POTHOVEN, G.L. Fahnenstiel, T.F. Nalepa, H.A. VANDERPLOEG, I. Tsehaye, R.M. Claramunt, and R.D. Clark. Changes in the Lake Michigan food web following dreissenid mussel invasions: A synthesis. Journal of Great Lakes Research 41(Supplement 2):15 pp. (DOI:10.1016/j.jglr.2015.08.009) (2015).
Using various available time series for Lake Michigan, we examined changes in the Lake Michigan food web following the dreissenid mussel invasions and identified those changes most likely attributable to these invasions, thereby providing a synthesis. Expansion of the quagga mussel (Dreissena rostriformis bugensis) population into deeper waters, which began around 2004, appeared to have a substantial predatory effect on both phytoplankton abundance and primary production, with annual primary production in offshore (N50 m deep) waters being reduced by about 35% by 2007. Primary production likely decreased in nearshore waters as well, primarily due to predatory effects exerted by the quagga mussel expansion. The drastic decline in Diporeia abundance in Lake Michigan during the 1990s and 2000s has been attributed to dreissenid mussel effects, but the exact mechanism by which the mussels were negatively affecting Diporeia abundance remains unknown. In turn, decreased Diporeia abundance was associated with reduced condition, growth, and/or energy density in alewife (Alosa pseudoharengus), lake whitefish (Coregonus clupeaformis), deepwater sculpin (Myoxocephalus thompsonii), and bloater (Coregonus hoyi). However, lake-wide biomass of salmonines, top predators in the food web, remained high during the 2000s, and consumption of alewives by salmonines actually increased between the 1980–1995 and 1996–2011 time periods. Moreover, abundance of the lake whitefish population, which supports Lake Michigan's most valuable commercial fishery, remained at historically high levels during the 2000s. Apparently, counter balancing mechanisms operating within the complex Lake Michigan food web have enabled salmonines and lake whitefish to retain relatively high abundances despite reduced primary production.
Mayer, A., R. Winkler, and L.M. FRY. Classification of watersheds into integrated social and biophysical indicators with clustering analysis. Ecological Indicators 45:340-349 (DOI:10.1016/j.ecolind.2014.04.030) (2014).
In this work, we classify watersheds in the US portion of the Great Lakes basin according to a wide range of social and environmental characteristics. Classified watershed indicators serve to provide organizing principles for prescribing effective management strategies and for developing regional scale monitoring and modeling efforts. Classifications also provide a means for synthesizing seemingly disparate ecological attributes into powerful indicators. We use a robust watershed classification scheme based oncluster analysis that integrates a set of 12 social and environmental factors chosen to reflect the state of water resources in the Great Lakes basin. We found five statistically distinct classified watershed indicators: Urban Centers, Intensive Agriculture, Cultivated Rural, Northwoods, and Lakes Destinations. Within these classifications, we distinguished relationships between impacts on water resources and bio-physical, demographic, land-use, and social characteristics of the landscape. We found that agricultural areas can be divided into those with high and low water impact, and that watersheds with considerable influence of seasonal homes are further distinguished into watersheds with inland lakes and relatively high socioeconomic status, contrasted with watersheds with wetlands and relatively low socioeconomic status.
MIEHLS, A.L.J., S.D. Peacor, L. Valliant, and A.G. McAdam. Evolutionary stasis despite selection on a heritable trait in an invasive zooplankton. Journal of Evolutionary Biology 28(5):1091-1102 (DOI:10.1111/jeb.12632) (2015).
Invasive species are one of the greatest threats to ecosystems, and there is evidence that evolution plays an important role in the success or failure of invasions. Yet, few studies have measured natural selection and evolutionary responses to selection in invasive species, particularly invasive animals. We quantified the strength of natural selection on the defensive morphology (distal spine) of an invasive zooplankton, Bythotrephes longimanus, in Lake Michigan across multiple months during three growing seasons. We used multiple lines of evidence, including historic and contemporary wild-captured individuals and palaeoecology of retrieved spines, to assess phenotypic change in distal spine length since invasion. We found evidence of temporally variable selection, with selection for decreased distal spine length early in the growing season and selection for increased distal spine length later in the season. This trend in natural selection is consistent with seasonal changes in the relative strength of non-gape-limited and gape-limited fish predation. Yet, despite net selection for increased distal spine length and a known genetic basis for distal spine length, we observed little evidence of an evolutionary response to selection. Multiple factors likely limit an evolutionary response to selection, including genetic correlations, trade-offs between components of fitness, and phenotypic plasticity.
Music, B., A. Frigon, B.M. LOFGREN, R. Turcotte, and J.F. Cyr. Present and future Laurentian Great Lakes hydroclimatic conditions as simulated by regional climate models with an emphasis on Lake Michigan-Huron. Climatic Change 130(4):603-618 (DOI:10.1007/s10584-015-1348-8) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150029.pdf
Regional climate modelling represents an appealing approach to projecting Great Lakes water supplies under a changing climate. In this study, we investigate the response of the Great Lakes Basin to increasing greenhouse gas and aerosols emissions using an ensemble of sixteen climate change simulations generated by three different Regional Climate Models (RCMs): CRCM4, HadRM3 and WRFG. Annual and monthly means of simulated hydrometeorological variables that affect Great Lakes levels are first compared to observation-based estimates. The climate change signal is then assessed by computing differences between simulated future (2041–2070) and present (1971–1999) climates. Finally, an analysis of the annual minima and maxima of the Net Basin Supply (NBS), derived from the simulated NBS components, is conducted using Generalized Extreme Value distribution. Results reveal notable model differences in simulated water budget components throughout the year, especially for the lake evaporation component. These differences are reflected in the resulting NBS. Although uncertainties in observation-based estimates are quite large, our analysis indicates that all three RCMs tend to underestimate NBS in late summer and fall, which is related to biases in simulated runoff, lake evaporation, and over-lake precipitation. The climate change signal derived from the total ensemble mean indicates no change in future mean annual NBS. However, our analysis suggests an amplification of the NBS annual cycle and an intensification of the annual NBS minima in future climate. This emphasizes the need for an adaptive management of water to minimize potential negative implications associated with more severe and frequent NBS minima.
NALEPA, T.F. Relative comparison and perspective on invasive species in the Laurentian and Swedish Great Lakes. Aquatic Ecosystem Health and Management 17(4):394-403 (DOI:10.1080/14634988.2014.972494) (2014).
The Laurentian Great Lakes and the Swedish Great Lakes both have a long history of being invaded by non-native species, although the total number reported in the former system far exceeds that in the latter. Until about the 1980s, non-native species that had the greatest ecosystem and/or socioeconomic impacts in both systems were controlled, or their negative impacts ameliorated by management actions; most prominent of these species were the Sea Lamprey and Alewife in the Laurentian Great Lakes, and Crayfish plague in the Swedish Great Lakes. In the 1980s, a number of species native to the Ponto- Caspian region were introduced into the Laurentian Great Lakes via the ballast water of transoceanic ships, and these species had significant ecosystem impacts, could not be controlled by management actions, and changed the way these lake resources were managed. Similar introductions have not occurred in the Swedish Great Lakes, but many of the same species that have impacted the Laurentian Great Lakes are spreading in European systems and in the Baltic Sea, and thus could pose an invasion risk to lakes in Sweden. Based on experiences in the Laurentian Great Lakes, it seems prudent to conduct a thorough assessment of these invaders relative to potential vectors of introduction for the Swedish Great Lakes. Also, an assessment of long-term monitoring programs is in order. Long-term data provides baseline information of the ecosystem and tracks ecosystem responses if indeed an invader becomes established.
NALEPA, T.F., D.L. FANSLOW, G.A. LANG, K. MABREY, and M. ROWE. Lake-wide benthic surveys in Lake Michigan in 1994-95, 2000, 2005, and 2010: Abundances of the amphipod Diporeia spp. and abundances and biomass of the mussels Dreissena polymorpha and Dreissena rostriformis bugensis. NOAA Technical Memorandum GLERL-164. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI, 21 pp. (2014). https://www.glerl.noaa.gov/pubs/tech_reports/glerl-164/tm-164.pdf
This technical report provides basic results of lake-wide, benthic surveys conducted in Lake Michigan in 1994-1995, 2000, 2005, and 2010 to assess temporal trends in the native amphipod Diporeia spp., the zebra mussel (Dreissena polymorpha), and the quagga mussel (Dreissena rostriformis bugensis). These surveys are an expansion of a continuing, monitoring program in the southern basin of the lake conducted by the Great Lakes Environmental Research Laboratory (GLERL) that examines trends in the abundance and composition of the entire macroinvertebrate community (Nalepa 1987, Nalepa et al. 1998). The GLERL program was initiated in 1980 with the original intent of assessing the response of the benthic community to phosphorus abatement efforts in the mid-1970s (Nalepa 1987). However, after D. polymorpha became established in the southwestern portion of the lake in 1989 (Marsden et al. 1993), the monitoring program detected several dramatic changes in the benthic community in the early 1990s. Diporeia began to systematically disappear, and D. polymorpha rapidly expanded and soon became dominant in the nearshore region (Nalepa et al. 1998). To determine if changes in the southern basin were also occurring throughout the lake, the monitoring program was greatly expanded in 1994-1995. Benthic sampling in these two years was conducted jointly with several other sampling programs in Lake Michigan: Environmental Monitoring and Assessment (EMAP) and Lake Michigan Mass Balance (LMMB). After 1994-1995, lakewide monitoring of Diporeia and Dreissena populations continued at 5-year intervals (i.e., 2000, 2005, and 2010) as part of a regular monitoring program at GLERL that supplemented the continued effort in the southern basin.
Niu, Q., M. Xia, E.S. RUTHERFORD, D.M. MASON, E.J. ANDERSON, and D.J. SCHWAB. Investigation of interbasin exchange and interannual variability in Lake Erie using an unstructured-grid hydrodynamic model. Journal of Geophysical Research - Oceans 120:21 pp. (DOI:10.1002/2014JC010457) (2015).
Interbasin exchange and interannual variability in Lake Erie’s three basins are investigated with the help of a three-dimensional unstructured-grid-based Finite Volume Coastal Ocean Model (FVCOM). Experiments were carried out to investigate the influence of grid resolutions and different sources of wind forcing on the lake dynamics. Based on the calibrated model, we investigated the sensitivity of lake dynamics to major external forcing, and seasonal climatological circulation patterns are presented and compared with the observational data and existing model results. It was found that water exchange between the western basin (WB) and the central basin (CB) was mainly driven by hydraulic and density-driven flows, while density-driven flows dominate the interaction between the CB and the eastern basin (EB). River-induced hydraulic flows magnify the eastward water exchange and impede the westward one. Surface wind forcing shifts the pathway of hydraulic flows in the WB, determines the gyre pattern in the CB, contributes to thermal mixing, and magnifies interbasin water exchange during winter. Interannual variability is mainly driven by the differences in atmospheric forcing, and is most prominent in the CB.
OBENOUR, D.R., A.D. GRONEWOLD, C.A. STOW, and D. Scavia. Using a Bayesian hierarchical model to improve Lake Erie cyanobacterial bloom forecasts. Water Resources Research 50(10):7847-7860 (DOI:10.1002/2014WR015616) (2014).
The last decade has seen a dramatic increase in the size of western Lake Erie cyanobacteria blooms, renewing concerns over phosphorus loading, a common driver of freshwater productivity. However, there is considerable uncertainty in the phosphorus load-bloom relationship, because of other biophysical factors that influence bloom size, and because the observed bloom size is not necessarily the true bloom size, owing to measurement error. In this study, we address these uncertainties by relating late summer bloom observations to spring phosphorus load within a Bayesian modeling framework. This flexible framework allows us to evaluate three different forms of the load-bloom relationship, each with a particular combination of statistical error distribution and response transformation. We find that a novel implementation of a gamma error distribution, along with an untransformed response, results in a model with relatively high predictive skill and realistic uncertainty characterization, when compared to models based on more common statistical formulations. Our results also underscore the benefits of a hierarchical approach that enables assimilation of multiple sets of bloom observations within the calibration processes, allowing for more thorough uncertainty quantification and explicit differentiation between measurement and model error. Finally, in addition to phosphorus loading, the model includes a temporal trend component indicating that Lake Erie has become increasingly susceptible to large cyanobacteria blooms over the study period (2002–2013). Results suggest that current phosphorus loading targets will be insufficient for reducing the intensity of cyanobacteria blooms to desired levels, so long as the lake remains in a heightened state of bloom susceptibility
POTHOVEN, S.A., and G.L. Fahnenstiel. Declines in the energy content of yearling non-native alewife associated with lower food web changes in Lake Michigan. Fisheries Management and Ecology 21:439-447 (DOI:10.1111/fme.12092) (2014).
Juveniles of non-native alewife, Alosa pseudoharengus (Wilson), were collected in Lake Michigan in 1998, 1999, 2010, 2011 and 2013 to evaluate changes in energy content during a period of major ecosystem changes. Consistent with historical data, energy content of yearling alewife declined from late winter into late spring and was at its lowest point in June. Energy density and length-adjusted, entire-body energy were lower in 2010, 2011 and 2013 than in 1998 and 1999. Energy losses over the first winter in the lake were more severe for the 2010 year class (56% decrease) than for the 1998 year class (28% decrease). Alewife diets in late spring of 2010–2013 reflected the loss of major prey such as Diporeia spp. and a shift towards lower energy prey. The recent decline in energy content of yearling alewife can be linked to recent changes in productivity and abundance of key components of the lower food web of Lake Michigan following the dreissenid invasion.
POTHOVEN, S.A., and G.L. Fahnenstiel. Spatial and temporal trends in zooplankton assemblages along a nearshore to offshore transect in southeastern Lake Michigan from 2007-2012. Journal of Great Lakes Research 41(Supplement 2):9 pp. (DOI:10.1016/j.jglr.2014.09.015) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150012.pdf
Zooplankton were collected at a nearshore (15 m depth), a mid-depth (45 m) and an offshore site (110 m) near Muskegon, Michigan during March–December in 2007–2012. On a volumetric basis, biomass was lower at the nearshore site relative to the mid-depth site, but overall biomass at the nearshore and offshore sites did not differ. Differences in zooplankton assemblages among sites were due largely to Diaptomidae, Limnocalanus macrurus, Daphnia galeata mendotae, Cyclops, and either Bosmina longirostris or Bythotrephes longimanus. Diaptomidae were the most abundant group, accounting for 56–66% of zooplankton biomass across sites. Herbivorous cladocerans accounted for 14–22% of zooplankton biomass across sites, with B. longirostris dominant at the nearshore site and D. g. mendotae dominant at the mid-depth and offshore sites. Bythotrephes was the most abundant predatory cladoceran at all sites although, at the nearshore site, it was only abundant in the fall. There was a higher percentage of large-bodied zooplankton groups in the offshore and mid-depth zones relative to the nearshore zone. Declines in zooplankton biomass relative to the 1970s have occurred across all sites. In addition to seasonal variation within a site, we noted annual variation, especially at the offshore site, with the zooplankton assemblage during 2007–2008 differing from that found in 2010–2012 due to increases in D. g. mendotae and Cyclops and decreases in B. longimanus and L. macrurus in 2010–2012.
POTHOVEN, S.A., and T.O. Hook. Feeding ecology of invasive age-0 white perch and native white bass after two decades of co-existence in Saginaw Bay, Lake Huron. Aquatic Invasions 10(3):347-357 (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150008.pdf
The diets and energy content of sympatric populations of invasive age-0 white perch Morone americana and native age-0 white bass Morone chrysops were evaluated in Saginaw Bay, Lake Huron following >20 years of coexistence. Fish were collected during July-November in 2009 and 2010 to assess seasonal and interannual patterns of diet composition, diet similarity, feeding strategy and energy density for the two species. The diet composition by weight of age-0 white bass was dominated by various zooplankton taxa, fish, or emergent insects, depending on the month and year. Although fish occasionally comprised a large fraction of the diet biomass, they were eaten by <24% of white bass each month. The diet composition of age-0 white perch shifted from one dominated by chironomids and other benthic macroinvertebrates in 2009 to one largely consisting of Daphnia spp. in 2010. There was more overlap in standardized diet assemblages in 2010 than in 2009 due to the increased importance of Daphnia spp. in white perch diets in 2010. Contrary to expectations, complete separation of diets was not a requirement that enabled the long-term coexistence of invasive white perch and native white bass in Saginaw Bay. Both age-0 white bass and white perch had a mixed feeding strategy with varying degrees of specialization and generalization on different prey. The inter-annual variation in prey, i.e., higher densities of zooplankton in 2009 and chironomids in 2010, is directly opposite of the pattern observed in white perch diets, i.e., diets dominated by chironomids in 2009 and zooplankton in 2010. Energy density increased from July into autumn/fall for both species suggesting that food limitation was not severe.
QIAN, S.S., C.A. STOW, and Y.K. Cha. Implications of Stein's paradox in environmental standard compliance assessment. Environmental Science & Technology 49(10):5913-5920 (DOI:10.1021/acs.est.5b00656) (2015).
The implications of Stein’s paradox stirred considerable debate in statistical circles when the concept was first introduced in the 1950s. The paradox arises when we are interested in estimating the means of several variables simultaneously. In this situation, the best estimator for an individual mean, the sample average, is no longer the best. Rather, a shrinkage estimator, which shrinks individual sample averages toward the overall average is shown to have improved overall accuracy. Although controversial at the time, the concept of shrinking toward overall average is now widely accepted as a good practice for improving statistical stability and reducing error, not only in simple estimation problems, but also in complicated modeling problems. However, the utility of Stein’s insights are not widely recognized in the environmental management community, where mean pollutant concentrations of multiple waters are routinely estimated for management decision-making. In this essay, we introduce Stein’s paradox and its modern generalization, the Bayesian hierarchical model, in the context of environmental standard compliance assessment. Using simulated data and nutrient monitoring data from wadeable streams around the Great Lakes, we show that a Bayesian hierarchical model can improve overall estimation accuracy, thereby improving our confidence in the assessment results, especially for standard compliance assessment of waters with small sample sizes.
ROCKWELL, D.C., S.J. JOSHI, and H. Wirick. Beach health information needs assessment: 9 years later -- results from follow-up survey. NOAA Technical Memorandum GLERL-163. NOAA, Great Lakes Environmental Research Laboratory, Ann Arbor, MI (2014). https://www.glerl.noaa.gov/pubs/tech_reports/glerl-163/tm-163.pdf
The Beach Health Interagency Coordination Team (BHICT) representing NOAA, USGS, USEPA, and the Centers for Disease Control (CDC) developed a survey for distribution to determine issues important to beach managers. The survey was distributed during Fall 2013 (August 28 to November 8). Responses were obtained when it was believed that federal funding from the BEACH Act would no longer be available. This survey is a follow-up to the Beach Health Research Needs Workshop held during the fall of 2005 at the Great Lakes Beach Association Conference in Green Bay (GLBA et. al. 2006, NOAA Technical Memorandum GLERL-138). The purpose of the survey is to assist BHICT member agencies in prioritizing their beach program based on input from the respondents on information, data, and tools they need to more effectively manage recreational water quality and beach health issues.
ROWE, M.D., E.J. ANDERSON, J. WANG, and H.A. VANDERPLOEG. Modeling the effect of invasive quagga mussels on the spring phytoplankton bloom in Lake Michigan. Journal of Great Lakes Research 41:17 pp. (DOI:10.1016/j.jglr.2014.12.018) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150011.pdf
The disappearance of the spring phytoplankton bloom in Lake Michigan has been attributed in some studies to the direct effect of quagga mussel filter-feeding. We applied a biophysical model to test whether the observed reduction in the spring bloom can be explained by direct effects of quagga mussel grazing. We developed a 1-D column biological model that simulated light and temperature limitation on phytoplankton growth, vertical mixing, and grazing by zooplankton and quagga mussels. We applied the 3-D finite volume coastal ocean model (FVCOM) to provide vertical mixing, with two scenarios of atmospheric forcing: (a) North American Regional Reanalysis (NARR) and (b) station interpolation using the Natural Neighbor Method. Simulated development of the spring bloom and formation of the deep chlorophyll layer in the early summer stratified period were consistent with observations. Increased strength of winter stratification (surface b 4 °C) in 1997 (cold spring) increased chlorophyll concentrations during March and April, compared to 1998, by reducing light limitation (reduced mixed-layer depth). Simulations with NARR forcing produced high-biased chlorophyll, resulting from low-biased wind speed and spring mixed layer depth. Simulated mussel filter feeding strongly reduced phytoplankton abundance when the water column was mixed to the bottom, but had little effect during periods of summer and winter stratification. These model simulations highlight the sensitivity of both phytoplankton growth and the impact of profundal quagga mussel filter-feeding to vertical mixing and stratification, which in turn is controlled by meteorological conditions.
ROWE, M.D., D.R. Obenour, T.F. Nalepa, H.A. VANDERPLOEG, F. Yousef, and W.C. Kerfoot. Mapping the spatial distribution of the biomass and filter-feeding effect of invasive dreissenid mussels on the winter-spring phytoplankton bloom in Lake Michigan. Freshwater Biology:15 (DOI:10.1111/fwb.12653) (2015).
1. The effects of the invasive bivalves Dreissena polymorpha (zebra mussel) and Dreissena rostriformis bugensis (quagga mussel) on aquatic ecosystems, including Lake Michigan, are a topic of current interest to scientists and resource managers. We hypothesized that the winter–spring phytoplankton bloom in Lake Michigan is reduced at locations where the fraction of the water column cleared per day by Dreissena filter feeding approached the net growth rate of phytoplankton, when the water column was not stratified. To test this hypothesis, we compared the spatial distribution of Dreissena filter-feeding intensity (determined from geostatistical modelling) to the spatial distribution of chlorophyll (determined from satellite remote sensing). 2. To map the spatial distribution of Dreissena biomass and filter-feeding intensity, we developed a geostatistical model based on point observations of mussel biomass measured in Lake Michigan in 1994/1995, 2000, 2005 and 2010. The model provided fine-scale estimates of the spatial distribution of biomass for the survey years and provided estimates, with their uncertainty, of total biomass lakewide and within subregions. The approach outlined could be applied more generally to map the distribution of benthic biota in lakes from point observations. 3. Total biomass of Dreissena in Lake Michigan, estimated from the geostatistical model, increased significantly over each five-year period. The total biomass in units of 106 kg ash-free dry mass (AFDM) (with 90% confidence interval) was 6 (4–8) in 1994/1995, 18 (14–23) in 2000, 408 (338–485) in 2005 and 610 (547–680) in 2010. From 1994/1995 to 2005, increases were observed in all regions of the lake (northern, central and southern) and in all depth zones (<30, 30–50, 50–90 and >90). However, from 2005 to 2010, for depths of <50 m, biomass declined in the northern region, remained constant in the central region and increased in the southern region; biomass continued to increase in all three lake regions for depths >50 m. 4. The filter-feeding intensity of Dreissena exceeded the benchmark spring phytoplankton growth rate of 0.06 day _1 in 2005 for depths <50 m (lakewide). In 2010, the filter-feeding impact exceeded 0.06 day _1 within depths <90 m (lakewide), which greatly increased the spatial area affected relative to 2005. A regression analysis indicated a significant relationship between the reduction in satellite-derived chlorophyll concentration (pre-D. r. bugensis period to post-D. r. bugensis period) and spatially co-located filter-feeding intensity (fraction of water column cleared per day) during periods when the water column was not stratified (December to April).
Sharma, S., (among 72 others), and G.A. LESHKEVICH. A global database of lake surface temperatures collected by in situ and satellite methods from 1985-2009. Nature Scientific Data:19 pp. (DOI:10.1038/sdata/2015.8) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150016.pdf
Global environmental change has influenced lake surface temperatures, a key driver of ecosystem structure and function. Recent studies have suggested significant warming of water temperatures in individual lakes across many different regions around the world. However, the spatial and temporal coherence associated with the magnitude of these trends remains unclear. Thus, a global data set of water temperature is required to understand and synthesize global, long-term trends in surface water temperatures of inland bodies of water. We assembled a database of summer lake surface temperatures for 291 lakes collected in situ and/or by satellites for the period 1985–2009. In addition, corresponding climatic drivers (air temperatures, solar radiation, and cloud cover) and geomorphometric characteristics (latitude, longitude, elevation, lake surface area, maximum depth, mean depth, and volume) that influence lake surface temperatures were compiled for each lake. This unique dataset offers an invaluable baseline perspective on global-scale lake thermal conditions as environmental change continues.
Smith, S.D.P., P.B. McIntyre, B.S. Halpern, R.M. Cooke, A.L. Marino, G.L. Boyer, A. Buchsbaum, G.A. BURTON, L.M. Campbell, J.J.H. Ciborowski, P.J. Doran, D.M. Infante, L.B. Johnson, J.G. Read, J.B. Rose, E.S. RUTHERFORD, A.D. Steinman, and J.D. Allan. Rating impacts in a multi-stressor world: A quantitative assessment of 50 stressors affecting the Great Lakes. Ecological Applications 25(3):717-728 (DOI:10.1890/14-0366.1) (2015).
Ecosystems often experience multiple environmental stressors simultaneously that can differ widely in their pathways and strengths of impact. Differences in the relative impact of environmental stressors can guide restoration and management prioritization, but few studies have empirically assessed a comprehensive suite of stressors acting on a given ecosystem. To fill this gap in the Laurentian Great Lakes, where considerable restoration investments are currently underway, we used expert elicitation via a detailed online survey to develop ratings of the relative impacts of 50 potential stressors. Highlighting the multiplicity of stressors in this system, experts assessed all 50 stressors as having some impact on ecosystem condition, but ratings differed greatly among stressors. Individual stressors related to invasive and nuisance species (e.g., dreissenid mussels and ballast invasion risk) and climate change were assessed as having the greatest potential impacts. These results mark a shift away from the longstanding emphasis on nonpoint phosphorus and persistent bioaccumulative toxic substances in the Great Lakes. Differences in impact ratings among lakes and ecosystem zones were weak, and experts exhibited surprisingly high levels of agreement on the relative impacts of most stressors. Our results provide a basin-wide, quantitative summary of expert opinion on the present-day influence of all major Great Lakes stressors. The resulting ratings can facilitate prioritizing stressors to achieve management objectives in a given location, as well as providing a baseline for future stressor impact assessments in the Great Lakes and elsewhere.
Soranno, P.A., (among 23 others), and C.A. STOW. Building a multi-scaled geospatial temporal ecology database from disparate data sources: Fostering open science through data reuse. GigaScience 4(28):15 pp. (DOI:10.1186/s13742-015-0067-4) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150032.pdf
Although there are considerable site-based data for individual or groups of ecosystems, these datasets are widely scattered, have different data formats and conventions, and often have limited accessibility. At the broader scale, national datasets exist for a large number of geospatial features of land, water, and air that are needed to fully understand variation among these ecosystems. However, such datasets originate from different sources and have different spatial and temporal resolutions. By taking an open-science perspective and by combining site-based ecosystem datasets and national geospatial datasets, science gains the ability to ask important research questions related to grand environmental challenges that operate at broad scales. Documentation of such complicated database integration efforts, through peer-reviewed papers, is recommended to foster reproducibility and future use of the integrated database. Here, we describe the major steps, challenges, and considerations in building an integrated database of lake ecosystems, called LAGOS (LAke multi-scaled GeOSpatial and temporal database), that was developed at the sub-continental study extent of 17 US states (1,800,000 km2). LAGOS includes two modules: LAGOSGEO, with geospatial data on every lake with surface area larger than 4 ha in the study extent (~50,000 lakes), including climate, atmospheric deposition, land use/cover, hydrology, geology, and topography measured across a range of spatial and temporal extents; and LAGOSLIMNO, with lake water quality data compiled from ~100 individual datasets for a subset of lakes in the study extent (~10,000 lakes). Procedures for the integration of datasets included: creating a flexible database design; authoring and integrating metadata; documenting data provenance; quantifying spatial measures of geographic data; quality-controlling integrated and derived data; and extensively documenting the database. Our procedures make a large, complex, and integrated database reproducible and extensible, allowing users to ask new research questions with the existing database or through the addition of new data. The largest challenge of this task was the heterogeneity of the data, formats, and metadata. Many steps of data integration need manual input from experts in diverse fields, requiring close collaboration.
STOW, C.A. The need for sustained, long-term phosphorus modeling in the Great Lakes. Journal of Great Lakes Research 41(2):315-316 (DOI:10.1016/j.jglr.2015.03.001) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150010.pdf
The 1978 Great Lakes Water Quality Agreement contained annual phosphorus load targets for each of the Great Lakes and larger bays. These targets were developed to combat eutrophication symptoms that resulted in the impairment of what we now refer to as ecosystem services. The targets were derived from several models of differing complexity and spatiotemporal resolution. As an ensemble those models reflected the knowledge and technology of the time. In the 1970s, this approach was new and somewhat of an experiment. Ecosystem management at this scale was unprecedented and the result was uncertain. However, it put the Great Lakes region at the forefront of innovative environmental management, and the approach has been widely copied in what we now refer to as Total Maximum Daily Loads. In the 1980s, there were signs that the experiment was working as eutrophication symptoms began to diminish. Unfortunately, these improvements were interpreted to indicate that the job was done. We declared success and moved on to other concerns such as toxic chemicals. The models were largely shelved, and the monitoring efforts supporting them were substantially reduced. At the time, such actions probably seemed sensible. Our view was that the lakes were fixed, and we could move on to other important concerns. This outlook was not confined to the Great Lakes community, but reflected the broader prevailing wisdom of the time.
STOW, C.A., Y.K. Cha, L.T. Johnson, R. Confesor, and R.P. Richards. Long-term and seasonal trend decomposition of Maumee River nutrient inputs to western Lake Erie. Environmental Science & Technology 49:3392-3400 (DOI:10.1021/es5062648) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150009.pdf
Cyanobacterial blooms in western Lake Erie have recently garnered widespread attention. Current evidence indicates that a major source of the nutrients that fuel these blooms is the Maumee River. We applied a seasonal trend decomposition technique to examine long-term and seasonal changes in Maumee River discharge and nutrient concentrations and loads. Our results indicate similar long-term increases in both regional precipitation and Maumee River discharge (1975−2013), although changes in the seasonal cycles are less pronounced. Total and dissolved phosphorus concentrations declined from the 1970s into the 1990s; since then, total phosphorus concentrations have been relatively stable, while dissolved phosphorus concentrations have increased. However, both total and dissolved phosphorus loads have increased since the 1990s because of the Maumee River discharge increases. Total nitrogen and nitrate concentrations and loads exhibited patterns that were almost the reverse of those of phosphorus, with increases into the 1990s and decreases since then. Seasonal changes in concentrations and loads were also apparent with increases since approximately 1990 in March phosphorus concentrations and loads. These documented changes in phosphorus, nitrogen, and suspended solids likely reflect changing land-use practices. Knowledge of these patterns should facilitate efforts to better manage ongoing eutrophication problems in western Lake Erie.
VanCleave, K., J. Lenters, J. WANG, and E. Verhamme. A regime shift in Lake Superior ice cover, evaporation, and water temperature following the warm El Nino winter of 1997-98. Limnology and Oceanography 59(6):1889-1898 (DOI:10.4319/lo.2014.59.6.1889) (2014). https://www.glerl.noaa.gov/pubs/fulltext/2014/20140058.pdf
Significant trends in Lake Superior water temperature and ice cover have been observed in recent decades, and these trends have typically been analyzed using standard linear regression techniques. Although the linear trends are statistically significant and contribute to an understanding of environmental change, a careful examination of the trends shows important nonlinearities. We identify a pronounced step change that occurred in Lake Superior following the warm El Nin˜o winter of 1997–1998, resulting in a ‘‘regime shift’’ in summer evaporation rate, water temperature, and numerous metrics of winter ice cover. This statistically significant step change accounts for most of the long-term trends in ice cover, water temperature, and evaporation during the period 1973–2010, and it was preceded (and followed) by insignificant linear trends in nearly all of the metrics examined. The 1998 step change is associated with a decrease in winter ice duration of 39 d (a 34% decline), an increase of , 2–3uC in mean surface water temperature (July–September averages), and a 91% increase in July–August evaporation rates, reflecting an earlier start to the summer evaporation season. Maximum wintertime ice extent decreased by nearly a factor of two, from an average of 69% of the lake surface area (before 1997–1998) to 36% after the step change. This reassessment of long-term trends highlights the importance of nonlinear regime shifts such as the 1997–1998 break point—an event that may be related to a similar shift in the Pacific Decadal Oscillation that occurred around the same time. These pronounced changes in Lake Superior physical characteristics are likely to have important implications for the broader lake ecosystem.
Wang, D., Y. Yang, J. WANG, K. Mizobata, and X. BAI. A modeling study of the effects of river runoff, tides, and surface wind-wave mixing on the eastern and western Hainan upwelling systems of the South China Sea, China. Ocean Dynamics 65:24 pp. (DOI:10.1007/s10236-015-0857-3) (2015).
This study investigates the variation of eastern Hainan (or Qiongdong) and western Hainan upwelling systems during the East Asia summer monsoon (EASM) season using a state-of-the-art finite-volume coastal model and reveals the impacts of tidal mixing, surface wind-wave mixing, and river runoff on the Hainan upwellings in terms of the spatial and temporal variations, intensification, and vertical structure. It is found that (1) river runoff, a stabilizer of the water column, suppresses the upwelling beneath it from reaching the surface, although strong upwelling still occurs in the lower layer of the water column; (2) tidal mixing, a mechanism of forming bottom mixed layer, promotes upwelling, leading to strengthening of the upwelling; (3) surface wind-wave mixing, a major mechanism for formation of the upper mixed layer and a sharp thermocline, inhibits the upwelling from crossing the thermocline to reach the surface; and (4) unlike the east coast upwelling, the upwelling on the west coast is tidally induced.
Wang, L., C.M. Riseng, L.A. Mason, K.E. Wehrly, E.S. RUTHERFORD, J.E. McKenna, C. Castiglione, L.B. Johnson, D.M. Infante, S.P. Sowa, M. Robertson, J.S. Schaeffer, M. Khoury, J. Gaiot, T. Hollenhorst, C. Brooks, and M. Coscarelli. A spatial classification and database for management, research, and policy making: The Great Lakes Aquatic Habitat Framework. Journal of Great Lakes Research 41(2):584-596 (DOI:10.1016/j.jglr.2015.03.017) (2015).
Managing the world's largest and most complex freshwater ecosystem, the Laurentian Great Lakes, requires a spatially hierarchical basin-wide database of ecological and socioeconomic information that is comparable across the region. To meet such a need, we developed a spatial classification framework and database — Great Lakes Aquatic Habitat Framework (GLAHF). GLAHF consists of catchments, coastal terrestrial, coastal margin, nearshore, and offshore zones that encompass the entire Great Lakes Basin. The catchments captured in the database as river pour points or coastline segments are attributed with data known to influence physicochemical and biological characteristics of the lakes from the catchments. The coastal terrestrial zone consists of 30-m grid cells attributed with data from the terrestrial region that has direct connection with the lakes. The coastal margin and nearshore zones consist of 30-m grid cells attributed with data describing the coastline conditions, coastal human disturbances, and moderately to highly variable physicochemical and biological characteristics. The offshore zone consists of 1.8-km grid cells attributed with data that are spatially less variable compared with the other aquatic zones. These spatial classification zones and their associated data are nested within lake subbasins and political boundaries and allow the synthesis of information from grid cells to classification zones, within and among political boundaries, lake sub-basins, Great Lakes, or within the entire Great Lakes Basin. This spatially structured database could help the development of basin-wide management plans, prioritize locations for funding and specific management actions, track protection and restoration progress, and conduct research for science-based decision making.
Wittmann, M., R. Cooke, J. Rothlisberger, E.S. RUTHERFORD, H. ZHANG, D.M. MASON, and D. Lodge. Use of structured expert judgment to forecast invasions by Bighead and Silver carp in Lake Erie. Conservation Biology 29(1):187-197 (DOI:10.1111/cobi.12369) (2014). https://www.glerl.noaa.gov/pubs/fulltext/2014/20140041.pdf
Identifying which nonindigenous species will become invasive, and forecasting their damages is difficult and presents a significant problem for natural resource management. Often, the data or resources necessary for ecological risk assessment are incomplete or absent, leaving environmental decision-makers ill-equipped to effectively manage valuable natural resources. Structured expert judgment (SEJ) is a mathematical and performance-based method of eliciting, weighting and aggregating expert judgments. In contrast to other methods of expert combination where equal weights are assigned to experts, SEJ weights each expert on the basis of his or her statistical accuracy and informativeness, and can be used when the information required for decision-making is sparse or debated. We used SEJ to forecast impacts of nonindigenous Asian carp in Lake Erie, where it is believed not to be established. Experts quantified Asian carp biomass, production, consumption and the impact to four fish species if Asian carp were to become established. According to experts, Asian carp can establish in Lake Erie with the potential to achieve biomass levels that are similar to the sum of biomasses for several fishes that are harvested commercially or recreationally. However, the impact of Asian carp on the biomass of these fishes is estimated by experts to be small, with little uncertainty. Impacts in tributaries and to recreational activities, water quality or other species were not addressed. SEJ can be used to quantify key uncertainties of invasion biology and also provide a decision support tool when the necessary information for natural resource management and policy is not available.
Wynne, T.T., T.W. DAVIS, R. Kelty, E.J. ANDERSON, and S.J. JOSHI. NOAA forecasts and monitors blooms of toxic cyanobacteria in Lake Erie. In Clear Waters. New York Water Environment Association, Inc., Syracuse, NY, 21-23 pp. (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150041.pdf
Blooms of cyanobacteria (commonly referred to as bluegreen algae) have been reported in Lake Erie as far back as the 1960s and 1970s. These blooms were nearly eliminated in Lake Erie by phosphorus abatement strategies in the 1970s that were part of the Great Lakes Water Quality Agreement, but re-emerged as a major water quality issue in the mid-1990s. The re-emergence of the blooms has been hypothesized to be a result of increases in agricultural pollution (nitrogen and phosphorus) into western Lake Erie. The role of the colonization of the invasive dreissenid mussels (a collective term for three similar mussel species) in promoting the re-emergence of the blooms is also being investigated.
XIAO, C., and Y. Zhang. Projected changes of wintertime synoptic-scale transient eddy activities in the East Asian eddy-driven jet from CMIP5 experiments. Geophysical Research Letters 42(14):6008-6013 (DOI:10.1002/2015GL064641) (2015). https://www.glerl.noaa.gov/pubs/fulltext/2015/20150040.pdfThe wintertime East Asian eddy-driven jet (EAEJ) responding to climate change in the 21st century is studied using model outputs from the Coupled Model Intercomparison Project phase 5 (CMIP5). Compared to the location displacement in oceanic eddy-driven jets, the magnitude change of synoptic-scale transient eddy activities, measured by eddy kinetic energy (EKE), is a more striking feature in EAEJ. An intensified EKE is projected unanimously by CMIP5 models, suggesting that potential strong winter storm events are likely to happen in East Asian midlatitude in a warming climate. The future change of EKE in EAEJ can be understood in terms of growing baroclinicity wave. The upper level EKE is highly correlated to the low-level static stability, Brunt-Väisälä frequency (BVF). CMIP5 models generally project an intensified upper level EKE with a reduced low-level BVF (ΔEKE_ΔBVF). Meanwhile, the enhancement of EKE is also constrained by its historical state (ΔEKE _EKE). Intermodel variabilities among CMIP5 models reveal a similar but weaker relationship between ΔBVF (or EKE) and ΔEKE, indicating relatively large model diversities and independencies among CMIP5 models.
Zhang, L., S. Wang, C. He, K. Shang, L. Meng, X. Li, and B.M. LOFGREN. A new method for instant correction of numerical weather prediction products in China. Science China - Earth Sciences 58(2):231-244 (DOI:10.1007/s11430-014-4957-6) (2015).
This paper presents a new correction method, “instant correction method (ICM)”, to improve the accuracy of numerical prediction products (NPP) and provide weather variables at grid cells. The ICM makes use of the continuity in time of the forecast errors at different forecast times to improve the accuracy of large scale NPP. To apply the ICM in China, an ensemble correction scheme is designed to correct the T213 NPP (the most popular NPP in China) through different statistical methods. The corrected T213 NPP (ICM T213 NPP) are evaluated by four popular indices: Correlation coefficient, climate anomalies correlation coefficient, root-mean-square-errors (RMSE), and confidence intervals (CI). The results show that the ICM T213 NPP are more accurate than the original T213 NPP in both the training period (2003–2008) and the validation period (2009–2010). Applications in China over the past three years indicate that the ICM is simple, fast, and reliable. Because of its low computing cost, end users in need of more accurate short-range weather forecasts around China can benefit greatly from the method.
Zhou, Y., A.M. Michalak, D. BELETSKY, Y.R. Rao, and R.P. Richards. Record-breaking Lake Erie hypoxia during 2012 drought. Environmental Science & Technology 49(2):800-807 (DOI:10.1021/es503981n) (2015).
Hypoxia has been observed in the central basin of Lake Erie for decades. To understand the impact of various controlling factors, we analyze a record of hypoxic extents for Lake Erie for 1985−2012 and develop a parsimonious model of their interannual variability. We find that the 2012 North American drought and accompanying low tributary discharge was associated with a record-breaking hypoxic event in Lake Erie, whereas a record-setting harmful algal bloom in 2011 was likely associated with only mild hypoxia. River discharge and the timing of nutrient input therefore impact western basin bloom growth and central basin oxygen demand in distinct ways that merit further investigation. Overall, April to June tributary discharge, May to July soluble reactive phosphorus loading, July wind stress, and June northwesterly wind duration explain 82% of the interannual variability of hypoxia, and discharge alone explains 39%, indicating that meteorological factors need to be considered in the development of nutrient management strategies, especially as both extreme precipitation events and droughts become more frequent under a changing climate.
Zhu, X., G. LIU, J. WANG, H. Wang, X. Bao, and W. Hu. A numerical study on the relationships of the variations of volume transport around the China Seas. Journal of Marine Systems 145:15-36 (DOI:10.1016/j.jmarsys.2014.12.003) (2015).
Three dimensional oceanic circulations in the North Pacific Ocean are simulated using the Regional OceanModel System (ROMS). The model very well reproduces the main oceanic circulation patterns and the hydrodynamic structures in the North Pacific Ocean, especially in the China seas. Eight transects around the China seas are selected to analyze volume transport and their relationships. The simulated mean volume transport and their standard deviations are in good agreement with previous studies and observations in the Taiwan Strait (TWS, 1.79 ± 0.96 Sv, 1 Sv ≡ 106 m3/s), East of Taiwan (PCM, 20.03 ± 5.19 Sv), Tokara Strait (TKS, 19.22 ± 3.22 Sv), Tsushima Strait (TUS, 2.14 ± 0.47 Sv), Luzon Strait (LUS, 4.57 ± 4.13 Sv), Karimata Strait (KMS, 1.28 ± 0.65 Sv), East of Luzon Island (ELI, 13.93 ± 5.31 Sv), and 137°E across the North Equatorial Current from 10°N to 20°N (137E, 44.0 ± 9.90 Sv). Three kinds of time scale variations (seasonal, sub-seasonal, intra-seasonal) were found in the volume transport through these transects with over the 95% significance level. The power spectrum density of the seasonal variation was almost one order of magnitude larger than the others for transects around the China seas. Coherency relationships among the volume transport through transects were analyzed. The results indicate that the seasonal time scale variations in volume transport around the China seas were dominated by the monsoon winds, but the Kuroshio along its pathway was relatively stable with small seasonal variation; the sub-seasonal time scale variations were associated with strong monsoon reversal winds; and the intra-seasonal variations were complex and weak, associating with local small scale winds and mesoscale eddy activities along the Kuroshio.
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Last updated: October 14, 2015 cmd